The invention relates to a bag which is manufactured from a rectangular pre-cut sheet of paper or foil, as well as a method for manufacturing, filling and sealing same. The bag is envisaged particularly for filling using powder-type filling materials. The packaging of powder-type filling materials into bags and the subsequent sealing of the bag seals creates a number of problems, which will be discussed in the following. In this connection, particularly for sealing paper bags, generally heat-sealing adhesive is applied to the sealing surfaces and these are heat-sealed together, or in the case of bags made of thermoplastic foil, the sealing surfaces are laid one on top of the other and thermally heat-sealed.
One problem which can arise is that it is very difficult to suppress dust build-up during filling, which leads to soiling of the system and impacts on the workplace; it can even lead to the risk of dust explosions. Such dust build-up therefore needs to kept as minimal as possible.
In order to keep dust build-up during the filling process within manageable limits, ventilated bags are widely used in which a valve outlet is glued into a floor section at one end. The disadvantage of such bags is the reduced filling speed caused by the ventilated cross section, which is restricted by the introduction of a filling nozzle a few centimetres in diameter. Finally, manufacture and recycling is made expensive using the additional valve outlets.
As long as open bags are used, the filling speed can be increased, however the whole sealing surface gets covered with dust during the filling process, so that the sealing process is not always performed perfectly. A surface covered with dust not only impedes gluing with heat-sealing adhesives, but also using heat-sealing thermoplastic foil surfaces.
An additional problem is the fact that bags filled with powder-type filling materials, which after filling are, for example, sealed using an interlocking or floor section fold, whose folding corners have micro openings which are connected via ducts to the inside of the bag, from which filling product can escape and, particularly with foodstuffs, through which harmful pests can find their way in.
From this initial position therefore, the exercise of the invention at hand is to provide a new type of bag as well as a method for its manufacture, filling and sealing, one which allows for filling with the utmost suppression of dust build-up, on the other hand which has a larger filling opening than ventilated bags for an increased rate of fill, and finally which facilitates sealing of the seal unimpeded by dust build-up.
The solution therefore lies in a bag according to the invention, which is defined in the independent patent claims as a semi-finished product (empty bag, filled and unsealed bag) as well as a finished product (filled and sealed bag); as well as a method for their manufacture and for their filling and sealing, which are shown in the independent claims relating to the method. Reference is made in the following to the wording on the content of the claims in respect of the semi-finished product, the product itself and the method.
An empty, flat bag set for transportation prior to the opening and filling processes according to the invention is distinguished in that the seal is formed by first and second sealing flaps, onto which pairs of gussets located at the endsxe2x80x94formed by one of the sealing collars lying on a plane created by the four sealing flapsxe2x80x94is connected to sealing corners. In this connection, during manufacture the first sealing flaps in relation to the bag walls, onto which they adjoin are folded outwards away from the bag opening, whilst second sealing flaps, in relation to the bag walls, onto which they adjoin and which generally form the shorter bag walls, are folded inwards onto the bag opening. The connection in accordance with the invention, ie gluing or heat-sealing together of the gussets on the ends of the sealing flaps already commences prior to filling the bag, so that hermetically perfect xe2x80x98sealingxe2x80x99 of the corner areas of the bag seal is guaranteed.
The way of folding over the first sealing flaps and the second sealing flaps in relation to the bag opening, in accordance with the invention, results in the relief opening cross section of the bag for filling not being reduced, as opposed to a standard open bag, since with this a considerable portion of the bag triangle has to be available outside the filling nozzle for holding and handling, so that the absolute relief opening cross section lies considerably under the theoretical one; in comparison with a ventilated bag however, a considerably larger filling cross section is available. The frame-like sealing collar created by the above mentioned sealing flaps lying on a plane with the option of introducing a filling nozzle onto it to create a circumferential sealing facility, in which an area outside the effective sealing line can be kept free of dust, so that perfect xe2x80x98sealingxe2x80x99 is possible in this area after the filling procedure is complete.
The sealing corners can be created, according to one preferred configuration, by a type of folded corner, for example such as one formed as previously described, when first the sealing flaps are folded away outwards at right angles from the first bag walls, and second sealing flaps of the second bag walls are folded inwards at right angles, ie coming to rest on the bag opening. In this connection, gussets separated by a folding edge on the ends of the first and second sealing flaps are made congruent, and in a position with the original surfaces on the same side of the initial material. The contacting gusset areas form the basis for the xe2x80x98sealingxe2x80x99 process of the sealing corners, in which these are carried out by gluing or by heat-sealing.
According to a second embodiment of the sealing corners, each of the first and second sealing flaps can be designed with transverse edges, ie independent of the respective adjacent sealing flaps. This creates the option of using sealing flaps of various widths. For example, the first sealing flaps can be designed considerably wider in order to make room for a finger hole. Sealing flaps of this kind can be manufactured using corner incisions on the initial material, which are basically in the corresponding positions of the previously mentioned folding edges. In this connection the gussets demarcated by the corner incisions at the ends of the first and second sealing flaps are made congruent and come into position with the original surfaces on the same side of the initial material. The contacting gusset areas form the basis for the xe2x80x98sealingxe2x80x99 process of the sealing corners, in which these are carried out by gluing or by heat-sealing.
In this connection the bag body can be shaped as a side folding bag, in which the second bag walls and the second sealing flaps are folded inwards between the perimeter areas of the first bag walls. The bag can however also be folded as a simple flat bag, so that the second bag wall and second sealing flaps are folded outwards beyond the perimeter areas of the first bag walls. In any event the flared open bag body, prior to and after filling, essentially has a rectangular cross floor section, which is determined by the position of the sealing corners and thereby the defined length of the first and second sealing flaps.
The bag floor can be of any chosen configuration, for example a standard folded floor. Simple linear gluing or heat-sealing like a seamed seal are however also possible.
On a flat bag where the second walls are folded outwards, in addition to the sealing flaps, adjoining areas of the bag wall can each be turned outwards or inwards, so that on each of the ends of the linear bag opening two larger triangular overlapping areas form the first sealing flap and the second sealing flaps, from which however the sealing corners can only be formed by sealed partial surfaces opposing each other at a distance. The surfaces lying in between, but not connected to one another, become rectangular cross section shapes as parts of the respective bag walls, upon flaring open the bag. On the empty, compressed bags set for transportation, the sealing flaps can be folded over, connected together by the sealing gussets and/or by the first bag walls formed by the sealing corners of these laid out in the same manner on top of one another on the plane, so that a flat stackable product is generated.
In the filling process a single bag is extracted from the stack of bags with a suitable device and brought into a vertically suspended position. In so doing the sealing collar is again folded out and brought into a configuration standing away at rightangles from the bag body. Furthermore, both the first sealing flaps act as to clamps to hold down the bag on the sealing collar. A bag held in this way can be conveyed in its suspended position, filled and, if appropriate, weighed. Upon filling the bag, this directly causes the bag to flare open.
After the filling process a cover sheet can be laid over the bag opening, which can be circumferentially sealed onto the sealing collar. In this connection, this kind of cover sheet can be laid out flat on the frame-like collar surface, or glued or heat-sealed by its longitudinal edges to the first sealing flap surface and glued or heat sealed by its transverse edges against folded sealing strips on the relief edges of the second sealing flaps. The transverse edges of the cover sheet can in this connection be likewise folded out as sealing edges. A bag in this state is completely hermetically sealed in its sealing area, so that the subsequent connection of the first sealing flaps, which by turning over onto one another as a kind of seamed seal, or by laying on top of one another with the insides to form a bag- or finger-seal, only aid to stiffen and reinforce, whilst a dust free xe2x80x98sealingxe2x80x99 process is ensured by manufacturing sealing corners prior to the and after the filling process by laying out the cover sheet.
In the process of manufacturing a bag according to the invention, two fundamental methods of processing are possible, dependent upon whether gluing with a heat-sealing adhesive or other adhesive, or a thermal heat-sealing of the bag material itself is envisaged.
When using an adhesive, an adhesive deposit is placed on a perimeter strip on one transverse edge of an essentially rectangular pre-cut sheet, which forms the sealing strips when subsequently folded over onto the double ended open bag body. Along one of the first longitudinal edges running the length of the floor area, adhesive deposits are attached depending on the desired kind of bag floor. In one sealing area running along the opposing longitudinal edge, adhesive deposits are applied to four gusset areas, which each form the demarcation between the first and the second sealing flaps of the finished folded bag and subsequently form the sealing corners. A joint line, which separates the subsequent bag body from the subsequent bag seal, demarcates the adhesive deposits in so doing. The gusset shaped adhesive deposits can be applied to the first sealing flaps or to the second sealing flaps. Normally the sealing area is of a consistent width, in which the sealing corners are generated by the much described turning over of the first sealing flaps onto the second sealing flaps along a joint line. As long as the first sealing flaps and the second sealing flaps are of different widths, or as long as a fold between the sealing flaps can be avoided, the longitudinal edge is designed with incisions, which run along one of the edges of the gusset-shaped adhesive deposits. The sealing flaps separated from one another by the incisions are made congruent by simply laying one on top of the other in otherwise the same manner.
As long as the bag is made of a material to be thermally heat-sealed, the steps for the double folding of a rectangular pre-cut sheet for manufacturing a bag body open at both ends, as well as for the creation of a bag floor, and the steps for connecting on top of one another, the first sealing flaps and the second sealing flaps are the same steps as previously mentioned, ie the systematic folding processes are the same, however if thermal heat-sealing is to be used for manufacturing the sealing strips after double folding the pre-cut sheet parallel to the transverse edges, and heat-sealing of the sealing corners after the laying on top of one another of the gussets on the ends of the first and second sealing flaps must be undertaken. In both cases these heat-sealing processes are likewise performed prior to the filling process on the dust-free bag, and are thereby of unimpaired quality.